Seal for a sterilizable bag and method of making the same

A sterilisable pouch comprising a seal between a first and a second polymeric sheet material, the first sheet material being sufficiently porous to permit gas or steam sterilisation but substantially impervious to bacteria, and the second sheet material being substantially gas impervious, and the second sheet material comprising at least an outer heat sealable layer, the seal comprising:

• a first thermal surface weld between the heat sealable layer of the second sheet material and the first sheet material;
• and
• a second thermal melt weld between at least the heat sealable layer of the second sheet material and the first sheet material, the thermal melt weld being narrower than the first weld and lying within the boundaries of the first weld.

A method of making a seal between a first and a second polymeric sheet material, the first sheet material being sufficiently porous to permit gas or steam sterilisation but substantially impervious to bacteria, and the second sheet material being substantially gas impervious, and the second sheet material comprising at least an outer heat sealable layer, the method comprising the steps of

• forming a surface thermal weld between the first and second sheet material;
• and
• forming a melt weld between the first and second sheet materials which is narrower than the first weld and which lies within the area of the first weld.